6-alkyl or 6-alkenyl-2 3-dimethoxy-5-hydroxy-1 4-benzoquinones and hydroquinones

ABSTRACT

THE DISCLOSURE DESCRIBES NOVEL 6-ALKYL AND 6-ALKENYL DERIVATIVES OF 2,3 - DIMETHOXY - 5-HYDROXY-1,4-BENZOQUINONES AND HYDROQUINONES WHICH ARE USEFUL AS ANTIOXIDANTS AND INHIBITORS OF SUCCINOXIDASE AND DPNH-OXIDASE IN MITOCHONDRIAL SYSTEMS. THE COMPOUNDS ARE PREPARED BY REACTING 2,3 - DIMETHOXY -5-HYDROXY-1,4-BENZOHYDROQUINONE WITH AN ALLYLIC ALCOHOL OR BY DECOMPOSING A DIACYLPEROXIDE IN THE PRESENCE OF 2, 3-DIMETHOXY-5-HYDROXY-1,4BENSONQUINONE.

6-ALKYL R 6-ALKENYL-2,3-DlMETHOXY-5-HY- DROXY-1,4-BENZOQUINONES AND HYDRO- QUINONES I Karl Folkers, 177 Gaya Road, Portola Valley, Calif.

94026; Joseph C. Catlin, 872 Colorado Ave., Palo Alto,

Calif. 94303; and Glenn Doyle Daves, Jr., 1530 SE.

- Blakeney, Beaverton, Oreg. 97005 I No, Drawing. Filed June 20, 1968, Ser. No. 738,393

' Int. Cl. C07c 49/74, 43/22 U.S Cl. 260- -396 R 13 Claims "ABSTR ACT OF THE DISCLOSURE The disclosure describes novel 6-alkyl and 6-alkeuyl derivatives of 2,3 dimethoxy -.hydroxy-1,4-benzoquinones and hydroquinones which are useful as antioxidants and inhibitors of succinoxidase and DPNH-oxidase in mitochondrial systems. The compounds are prepared by reacting 2,3 dimethoxy S-hydroxy-l,4-benzohydroquinone with an allylic alcohol or by decomposing a diacylperoxide in the presence of 2,3-dimethoxy-5-hydroxy-1,4- benzoquinone. a

BAckGRoU D OF THE INVENTION This invention relates to novel 2,3 dimethoxy S-hydroxy-1',4-benz0quinones and hydroquinones and to the process for preparing the same. More particularly, the invention relates to 6-alkyland 6-alkenyl derivatives of such benzoquinones, and especially those compounds containing isoprenoid substituents in the 6-position.

The compounds of this invention are structurally similar to the 2,3 dimethoxy.- 5-methyl-6-alkyl-1,4-benzoquinones described and claimed in US. Pat. application Ser. No. 757,464, filed Aug. 27, 1958 in the name of Folkers et al., now abandoned. However, the present S-hydroxy compounds differ significantly from the S-methyl compoundsof said prior application. Generally the S-methyl compounds have activity similar to that of coenzyme Q and the S-hydroxy compounds do not have activity in the'two enzyme systems requiring the functionality of coenzyme Q. In even greater contrast, the S-hydroxy compounds are antagonists of coenzyme Q. The antioxidant activity of the S-hydroxy compounds in the absence of the coenzymatic activity of the S-methyl compounds makes them particularly useful antagonists.

SUMMARY OF THE INVENTION The novel compounds of this invention are benzoquinones and hydroquinones which may be represented by the structures 0 OH 1 I l CH O -OH and CH30 OH C1130 R CHsO- R ll 0 I OH Patented Feb. 22, 1972 Ice preferably from about 1 to 10; alkenyl groups, such as groups containing the structures or (CH=CH-). Specific alkenyl groups which may be present include those of the structure and [CH CH=C(CH )CH ],,H wherein y is an integer less than x and z is an integer less than n. Preferably each of y and n Will be of the order of about 1 to about 5. In such alkenyl groups, n will be at least 2. It will be understood that the above exemplary representations do not specify the order of saturated and unsaturated moieties in the group R, any arrangement of saturated and unsaturated linkages being suitable. The group R may bear one or more inert substituents, preferably hydrocarbon substituents such as cycloalkyl and cycloalkenyl groups.

In accordance with the above description, R can be amyl, hexyl, heptyl, octyl, decyl, dodecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl eicosyl tetracosyl, pentacosyl, cyclohexyloctyl, cyclohexenyoctyl, hexenyl, octenyl, decenyl, dodecenyl, tetradecenyl, heptadecenyl, eicosenyl, tricosenyl, tetracosenyl, decadienyl, dodecadienyl, heptadecadienyl, dodecatrienyl, pentadecatrienyl, heptadecatrienyl, nonadecatetrenyl, nonadecapentenyl, geranyl, farnesyl, tetraprenyl, solanesyl, decaprenyl, phytyl, octahydrotetraprenyl, etc. The preferred R groups are those containing isoprenoid substituents.

The compounds of the invention can be prepared from known and available starting materials. For example, 2,3-dimethoxyphenol is converted to 2,3-dimethoxy1,4- benzoquinone, which is in turn used to prepare 1,4,5-trihydroxy 2,3 dimethoxybenzene. The last-named compound or the corresponding quinone is converted into the compounds of the invention by 6-alkylation. The reaction sequence is illustrated as follows:

on or! on I l I 0 ca o CH3O 0H 1 0H cu o- 0530- l I I in a or: on

effected by acid-catalyzed reaction of the trihydroxy alcohol,

Such alcohols may be natural products such as phytol or geranol, or synthetic alcohols such as 3,7-dimethyl-1- octen-3-ol; 3,7,11-trimethyl-1-dodecen-3-01; 3,7,11,15,19- pentamethyl 1-eicosen-3-ol; 3,7,11,15,19,23-hexamethyl- 1-tetracosen-3-ol and 3,7,1l,15,19,23,27-heptamethyl-1- octacosen-3-ol. The reaction is carried out in the presence of acidic condensing agents such as potassium acid sulfate, zinc chloride, oxalic acid, boron trifiuoride, and aluminum chloride; this will effect the condensation between the hydroquinone III and the alcohol. The condensation is carried out in an inert solvent such as dioxane, ether, or dimethoxy ethane at a temperature of from about when aluminum chloride is used as the condensing agent to 75 when potassium acid sulfate is used. Boron trifiuoride works well at room temperature The reaction may be carried out in the open but will be conducted in an inert atmosphere (nitrogen) where it is desired to obtain the product in the hydroquinone form.

Non-isoprenoid R groups are most readily prepared by decomposing the corresponding diacyl peroxide,

in the presence of quinone compound IV. If desired, all or a part of the unsaturated bonds in the substituent R may be hydrogenated by catalytic hydrogenation.

The products are preferably purified by chromatographic separation of the compounds in either the hydroquinone or quinone form. Generally, the hydroquinones will be air-oxidized to the quinones during work-up. Location of the desired compounds is facilitated by the fact that they are violet in color on silica gel G, yellow in organic solvent solution, and red in solid form. The appropriate band of chromatographic medium can thus be readily located, physically separated, andeluted with a suitable solvent such as ether or hexane-ether.

The compounds are useful antioxidants since, in vivo, the quinone form is reduced and is in biological equilibrium with the hydroquinone. The S-hydroxybenzoquinones are useful as inhibitors of the succinoxidase and DPNH-oxidase systems of intact mitochondrial systems or those extracted to remove coenzyme Q and are thus useful in studies of the vitamin-like activity of coenzyme Q. The compounds are useful in inhibiting oxidative rancidity which occurs during the storage and handling pf oleaginous materials such as vegetable and animal oils and fats. The addition of an amount of 0.05 to about 4% by weight of the compounds of the invention to an oleaginous material such as corn oil will inhibit the formation of peroxides which are indicative of the occurrence of rancidity.

4 Preparation, purification and properties of representative compounds of the invention are illustrated by the following examples It will be understood, however, that the invention is not limited to the specific embodiments described.

EXAMPLES 1-7 Isoprenylation of 2,3-dimethoxy-5-hydroxy- 1,4-benzohydroquinone To a solution of 1.9 g. (0.01 mole) of 2,3-dimethoxy- S-hydroxy-1,4-benzohydroquinone in 25 ml. of dry dioxane there is added an equivalent amount of the appropriate isoprenoid alcohol( in cases where the alcohol is expensive or difiicult to obtain, less than an equivalent amount is used). The dioxane solution is protected by a drying tube and is stirred vigorously while 1.5 ml. of redistilled boron trifiuoride etherate is added dropwise. The reaction mixture is stirred for two hours and then poured into ml. of water. The product is extracted into ether, and the ether solution is dried over sodium sulfate, filtered and concentrated under reduced pressure. The residue is purified by layer chromatography on silica gel plates (20 cm. x 20 cm. x 1 mm.) using 4:1 benzenemethanol as the solvent. The violet band is scraped and eluted with ether to obtain the desired 2,3-dimethoxy-S-hydroxybisoprenoid-1,4-benzoquinone. Alternatively, the reaction product is purified by'column chromatography on silica gel, using hexane-ether as the solvent.

Following this procedure, the 6-geranyl, farnesyl, tetraprenyl, solanesyl, decap renyl, and phytyl compounds are prepared. The -octahydrotetraprenyl' derivative is made by dissolving 0.26 g. of the G-phytyl compound in ethanol and hydrogenating at 35 psi of hydrogen in the presence of 0.1 g. of 10% Pd/C, then purifying as above.

EXAMPLES 8-12 Alkylation of 2,3-diniethoxy-5-hydroxy- 1,4-benzoquinone To a dioxane solution of 5 g. of 2,3sdimethoxy-5- hydroxy-1,4-benzohydroquinone there is added-7 g. of silver oxide, and the resulting mixture is shaken for one hour. The reaction mixture is then filtered and concentrated under reduced pressure. The quinone so obtained is combined with 0.05 .mole of the appropriate diacylperoxide in 100 ml. of acetic acid and heated overnight on a steam bath. Acetic acid is distilled ofi tinder reduced pressure and the residue is taken up iii hexane, placed on a silica gel column, and eluted with increasing fractions of ether in hexane. Alternatively, the compounds are purified by layer chromatography on silica gel'as described in Examples 1-7.

By this technique, there are prepared the 6 -penta-decyl, heptadecyl, nonadecyl, (8', 11', 14'-heptadecatrienyl), and (8'-cyclohexyl) octyl derivatives of 2,3-dimethoxy-5- hydroxy-l,4-benzoquinone.

The structures of the noted compounds are demonstrated by the spectra of the isolated products, as shown in Table I, in which UV spectral data and NMR data for the compounds are tabulated. Akylation on carbon and not on oxygen is indicated by the absence of a ring proton and TABLE I.SPECTRAL DATA OF 2,8-DIMETHOXY-5-HYDROXY-iS-RJABENZOQUINONES UV etlianol NMR max. B (Hip) Vinyl Methoxyls Benzylic Alkyl Geranyl 298 5.0 (m) 6.00 (e) 6 Farnesyl 297 6.0 (m) 6.00 (s) 6 TetraprenyL. 297 5.0 (m) 6.00 (s) 6. Solanesyl 297 4.98 (m)... 6.00 (s) 6. Decaprenyl 4. 00 (s 6. Phyt l 4. (t) 5.98 (s) 6. Oetohydrotetrapreny .98 (s 6. Penta ecyl 6.00 (s) 6. Heptadecyl 6.00 (s) 6.15 Nonadecyl 01 299 6. (s) 290 5.74 (m) 5.051(3) 297 6.01 (s) 5 The absorption of the benzylic protons falls within the range of the absorption of the alkyl protons.

the presence of benzylic protons at tau 6.9-7.7 in the 5. A compound according to claim 1 wherein R is NMR spectra; these protons would be found at tau 5.3- solanesyl. 5.9 when the carbon is attached to oxygen. NMR spectra 6. A compound according to claim 1 wherein R is are obtained using carbon tetrachloride solutions with a decaprenyl. Varian Associates HR 100 spectrometer. In Table I, values 5 7. A compound according to claim 1 wherein R is are in tau units and the letters in parentheses refer to phytyl. peak shape: s=singlet, d=doublet, t=triplet, m=mul- 8. A compound according to claim 1 wherein R is tiplet. octahydrotetraprenyl.

The activity of the compounds as inhibitors of suc- 9. A compound according to claim 1 wherein R is cinoxidase and DPNH-oxidase in intact or coenzyme 1O pentadecyl. Q-extracted mitochondrial systems is shown by the data in 10. A compound according to claim 1 wherein R is Tables 11 and HI. heptadecyl.

TABLE II.HYDROXYQUINONES IN THE DPNH-OXIDASE AND SUCCINOXIDASE SYSTEMS Intact mitochondrial systems DPNH-oxidase Succinoxidase Specific Specific Specific Specific Addition B activity b Percent activity b Percent activity b Percent activity Percent None 0.396 65 0. 406 50 0.452 85 0. 366 80 CoQm s s 0. 596 100 0. 794 100 0. 533 100 0. 445 100 CcQm plus 2,3-dimethoxyydroxyrnesy ,4-benzoquino 0. 608 75 0. 309 60 ne COQ o plus 2,3-dimethoxy-5-hydroxy-6-solanesy1-1,4-benzoqumone 60 0. 164 30 CoQio plus 2,8-dimethoxy-fi-hydroxy-G-phytyl-l 4-benzoqninone s 129 30 CoQw plus 2,3-dimethoxy-dhydroxy-G-dihydr benzoquinone 50 0. 096 20 CoQio plus 2,3-dimethoxy--hydroxy benzoquinone 50 0.117

B In each case, 100 my moles of the qninones is added. b atoms of oxygenlminJmg. of protein.

TABLE III.2,3-DIMETHOXY-5HYDROXY-o-PHYTYIAA-BENZOQUINONE (HPB) IN THE DPNH-OXIDASE AND SUCOINOXIDASE SYSTEMS Enzyme activity DPNH-oxidase Succinoxidase Extracted Intact mito- Intact mitomitochondria chondrla chondria Specific Specific Specific Addition activity Percent activity Percent activity Percent No O. 056 0 0.392 50 0. 296 95 CoQio (100 mumoles)- 0. 344 100 0.813 100 0.308 100 HPB (100 mpmoles) 0.168 20 0.0025 0 CoQm (100 mumoles) plus HP 0. 256 70 0.569 70 0.098 CoQw (100 mnmoles) plus HPB (100 m moles) 0. 188 0.306 40 0. 048 15 CoQm (100 mpmoles) plus HPB (200 mumoles) 0. 041 0 0.066 10 0. 035 10 OoQio (200 mumoles) plus HPB mumoles) 0.700 85 0.093 30 e natoms of oxygenlminJmg. of protein. b When the enzyme is extracted, any respiration is assumed to be due to unextracted coenzyme Q. The blank is subtracted from each value obtained.

What is claimed is: 11. A compound according to claim 1 wherein R is 1. A compound selected from the group consisting of 0 nonadecyl.

12. A compound according to claim 1 wherein R is 9 2 8 ',1 1 l4'-heptadecatrienyl.

13. A compound according to claim 1 wherein R is (ll-I 0 0H and OH 8'-(cyclohexyl)octyl. ca o R cn o R I References Cited 0 UNITED STATES PATENTS wherein R is an alkyl or alkenyl group having 10 to 50 3,030,334 3/ 1963 ofi r et a1 260396 carbon atoms, 3,349,113 10/1967 G! et a1 260-396 2. A compound according to claim 1 wherein R is geranyL LORRAINE A. WEINBERGER, Primary Examiner 3. A compound according to claim 1 wherein R is L, A, THAXTON, A i t t E min r farnesyl.

4. A compound according to claim 1 wherein R is 5 US. Cl. X.R. tctraprenyl. 260-613 D, 999 

